On the afternoon of October 27, 1958, Chairman Mao visited the Chinese Academy of Sciences’ Exhibition of Achievements in the Natural Sciences Leap Forward at Zhongguancun. During the tour, he spotted Comrade Qian Xuesen and had a conversation with him.

……The Chairman noticed Comrade Qian Xuesen and said, “We last met in 1956 at a CPPCC meeting. That year, the whole country was full of vigor; we still had it going into the following spring, but afterward spirits began to flag. Then came the Hungarian incident, followed by the anti-“leftist” campaign against overambition—truly a sinister wind. Calling it a ‘saddle-shaped’ curve is quite apt.”

Comrade Qian Xuesen replied, “I don’t understand agriculture. I merely made a rough calculation based on solar energy. As for how to actually achieve that figure, I have no idea. Moreover, we have since discovered that even that method of calculation contained errors.”

The Chairman laughed and remarked, “So you were just shouting out a bold claim too!” This remark set everyone off in hearty laughter.

However, the Chairman went on to say, “Your general view is correct. The problem of irrigation has now been basically solved. The main lessons of high yields lie in deep plowing, fertilization, and close planting. Deep plowing allows for greater absorption of sunlight and enables the roots to take up more organic matter, which in turn promotes more abundant and faster growth. In the past, people practiced shallow tillage and extensive cultivation with meager returns; today, we need deep, meticulous cultivation and less land sown for greater harvests. This saves labor, fertilizer, and water resources. The land thus freed up can be used for afforestation, fallow periods, or industrial development.”